Sergio Martinez KOs Paul Williams early

ATLANTIC CITY, N.J. -- Sergio Martinez and Paul Williams landed punch after punch a year ago in an instant classic, one of those rare occasions when two of the best boxers in the world come together to create something special.

Their rematch Saturday night didn't last nearly as long, and only one punch mattered.

Martinez landed a devastating left hook early in the second round, knocking out one of boxing's most feared punchers while retaining his middleweight championship.

The sudden outcome left a lively crowd at Boardwalk Hall in stunned silence.

"I started to attack, and when I did, we knew he was going to make a mistake, because he always makes mistakes," Martinez said. "He left me a lot of room to come in and hit him."

Williams was looking to land his own hook and instead walked right into the punch, which landed flush on the chin and sent the challenger face-down onto the canvas. Martinez immediately ran across the ring to celebrate while doctors rushed in to tend to Williams.

It took several minutes before he finally got to his feet, and by that point, ring announcer Michael Buffer was already announcing the end at 1:10 of the second round.

"I got caught with a punch," Williams said while being tended to by paramedics.

In their first encounter last December, Martinez and Williams traded knockdowns in the first round before trading blows for 11 more. Williams ultimately won that fight by close and somewhat controversial decision, and Martinez had been saying all along that he planned to make sure this one didn't end up in the judges' hands.

He sure accomplished that.

"I didn't want the judges to rob me this time," said the 35-year-old Martinez, one of the rare fighters entering his prime this late in his career.

"He said, 'I'm going to knock him out. The fight is not going to go seven rounds, I'm going to knock him out," Martinez promoter Lou DiBella said, unable to contain a smile. "I was worried like a maniac and he said, 'No, I'm knocking him out. Relax."

The only real drama came before the fighters made their way to the ring, when DiBella was furious that his guy as champion was forced to work out of the blue corner. That side of the ring had not delivered a winner all night, at least until the main event.

"I mean, in my heart, I thought he was going to win, but that was one of the great knockout punches of another great fighter I've ever seen," DiBella said. "Williams is a brilliant fighter, but Martinez's speed and angles, that punch -- that punch would have knocked anyone out."

Despite their first fight becoming an instant classic, the rematch took plenty of time and patience to put together. Martinez (46-2-2, 25 KOs) upped the ante by claiming the middleweight title from Kelly Pavlik in blood decision earlier this year, while Williams (39-2) held out hope of landing a big payday at welterweight against the likes of Manny Pacquiao, Floyd Mayweather Jr. or Shane Mosley.

When it become apparent that those fights would never happen, promoter Dan Goossen agreed to the rematch with Martinez, getting his fighter back in the spotlight on an HBO telecast.

No wonder he was reluctant to make the rematch.

While neither Martinez nor Williams is fond of the other, there was more acrimony than usual in the lead-up to this one because Williams insisted on a catch weight of 158 pounds -- two under the middleweight limit -- since he'd been training to fight at 147 pounds. Martinez countered by saying he'd be "ashamed" to ask for a catch weight if he was challenging for a world title.

The two pounds sure didn't seem to make much difference.

Martinez looked faster and smoother than Williams, and landed several crisp punches in the opening round, including a flurry on the ropes that gave him the edge on the scorecards. Then he came out the next round and almost seemed to bait Williams into throwing a wide punch.

When it came, Martinez was ready, and the end happened in a flash.

Martinez said he wants to fight two or three more times before calling it a career, especially after landing a payday of a little over a $1 million for barely 4 minutes of work.

He mentioned as possible candidates Pacquiao, considered the best fighter in the world, and Mayweather, who long held the same mantle. But most fans are hopeful that those two eventually will meet and, in any case, Martinez probably still doesn't have enough name recognition beyond the most ardent boxing fans to lure one of them into the ring.

"If you're Pacquiao, would you go near him? You think Mayweather will fight him?" DiBella said. "We're going to have a problem making the next fight because that's how good he is."

DiBella floated the idea of another rematch with Williams, now that Martinez has squared the series at one win apiece. There was discussion of a trilogy even before Saturday night, and it could be the best opportunity available to either fighter.

"I want to listen to all offers," Martinez said, "and see what comes my way."